The present invention is directed to a precast concrete traffic barrier. More specifically, the present invention relates to a precast concrete traffic barrier element and a method of constructing a traffic barrier on a face of a structure such as a retaining wall.
Traffic barriers are used on roads to restrain a moving vehicle from crossing into an oncoming lane of traffic or from driving off a traffic surface. The traffic barrier is usually anchored in the traffic surface to absorb an impact from the moving vehicle and to resist overturning of the barrier due to the impact. Many times, an impact receiving side of the traffic barrier is profiled (e.g., a concrete traffic barrier having a New Jersey profile) for deflecting or redirecting the moving vehicle back onto the road.
Traffic barriers are especially useful on elevated structures, such as bridge and highway ramps, in order to restrain an incident vehicle from crashing through the barrier and falling from a precipitous edge of the elevated road. Elevated roads are often constructed by piling earth or soil onto metal reinforcements to form a frictionally stabilized composite earth structure for supporting and elevating the road (e.g., see U.S. Pat. No. 3,686,873). The composite earth structure may include a wall face of interfitted panels for covering the sides of the composite earth structure. Often times, an edge of the traffic surface is required to be close to the wall face and in such cases, there is a need for a traffic barrier positioned adjacent to the wall face. If there exists a sufficient space between the face and the edge of the traffic surface, then the traffic barrier may be positioned and adequately anchored without interfering with the wall face. However, a problem exists in constructing and anchoring the traffic barrier when the traffic barrier is supported on or closely adjacent to the face of a retaining wall, such as the composite earth structure.
In an effort to construct and adequately anchor a traffic barrier supporrted on a wall face of a stabilized earth structure, a concrete traffic barrier has been cast-in-place on a top edge of the face so as to be integral with the wall face. During construction, scaffolding is erected adjacent to the face and workmen on the scaffolding construct forms for the traffic barrier on the top edge of the face. Reinforcing bars may be placed in the forms to strengthen the device. Concrete is then poured into the forms and allowed to set. The forms are then removed and a subterranean counterweight slab is cast-in-place to anchor the barrier.
Alternatively, a post and rail traffic barrier has been embedded in a precast concrete wall cap. The present cap is supported on an upper surface of the soil inside of the wall face. A lip extending from the cap overhangs the vertical face and a gap exists between the lip and a top edge of the face. An in situ subterranean extension of the cap is then cast-in-place to anchor the cap with the post and rail traffic barrier situated thereon.
While the above-described cast-in-place traffic barrier is adequately anchored, such a barrier requires the construction of forms in which the concrete is poured and allowed to set. The use of forms, however, is costly and time consuming since numerous workmen are required to build the forms, place the steel, and pour the concrete. Further, scaffolding must be erected adjacent to the face in order to support the workmen building and removing the forms. As a result, the construction of the cast-in-place traffic barrier is a slow and labor-intensive operation.
The construction of the above-described precast wall cap involves less form-work than the cast-in-place traffic barrier, but it still requires forms for constructing the in situ extension of the wall cap. Further, the wall cap does not rest on the top edge of the face, but is supported on the soil inside of the face. As a result, the soil inside of the face and underneath the cap must be graded in order to properly position the cap. The precast wall cap also employs a post and rail traffic barrier which is designed to absorb impact from an incident vehicle, rather than redirect the vehicle.
The present invention relates to a traffic barrier for use as a safety device to resist accidental passage of an incident vehicle over a precipitous edge. The traffic barrier includes a wall structure defining a top edge having both a wall face fashioned from interfitted facing elements and a traffic surface. A plurality of precast concrete traffic barrier elements are positioned in an end-to-end relationship along the top edge. In this manner, the need for on-site forms is eliminated since the element is precast. Scaffolding is also eliminated since the precast element can be lifted into position by a crane situated on the traffic surface. In addition, the precast barrier element, unlike the present wall cap, rests on the top edge of the wall face so that the element is properly positioned without grading. As a result, the precast traffic barrier of the present invention requires less labor and time to construct than both of the above-described traffic barriers.
Each barrier element has a side facing the traffic surface with a cross-sectional profile for redirecting an incident vehicle toward the traffic surface. A bottom surface of each barrier element has a longitudinally extending channel therein which is sized to receive the top edge of the wall structure for partially supporting the barrier element. The barrier element has a length sufficient to cover at least one vertical joint between interfitted facing elements in order to laterally stiffen the wall face. An attachment mechanism toward the traffic surface side of the wall structure connects the barrier element with a cast in situ counterweight which engages the attachment mechanism of at least two barrier elements to stiffen the barrier while counterbalancing vehicle impact forces. As a result, the precast concrete traffic barrier according to the present invention has a greater impact resistance than post and rail traffic barriers.
The method of constructing a traffic barrier on a top edge of a wall face of an earth structure having a traffic surface thereon includes the step of positioning a precast concrete traffic barrier element on the wall face with the top edge of the wall being received within a longitudinally extending channel in a bottom surface of the barrier element. In positioning the barrier element, the barrier element is partially supported on the top edge of the wall face with anchoring bars projecting from the barrier element toward the traffic surface. The anchoring bars are then anchored in a cast in situ counterweight positioned adjacent to the traffic surface.
Many objects and advantages derived from the present invention will become apparent to those skilled in the art from this specification.